Integrated circuits, liquid crystal display (lcd) drivers, and systems

ABSTRACT

An integrated circuit includes a digital-to-analog converter (DAC) circuit including at least one first channel type digital-to-analog converter (DAC) and at least one second channel type DAC. The integrated circuit further includes a plurality of sample and hold (S/H) circuits, each of the plurality of S/H circuits being coupled with a single DAC of the DAC circuit. A number of the at least one first channel type DAC is different than a number of the at least one second channel type DAC.

PRIORITY CLAIM

The present application is a continuation of U.S. application Ser. No.13/466,608, filed May 8, 2012, which is a continuation of U.S.application Ser. No. 12/762,535, filed Apr. 19, 2010, now U.S. Pat. No.8,188,898, issued May 29, 2012, which claims the priority of U.S.Provisional Patent Application No. 61/232,200, filed Aug. 7, 2009, whichare incorporated herein by reference in their entireties.

RELATED APPLICATION

The present application relates to U.S. application Ser. No. 12/762,508,filed Apr. 19, 2010, commonly owned and assigned, and herebyincorporated by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to the field of semiconductorcircuits, and more particularly, to integrated circuits, liquid crystaldisplay (LCD) drivers, and systems.

BACKGROUND

Applications for semiconductor devices may use power devices, such as aliquid crystal display (LCD) driver. An LCD driver can operate at a highvoltage to drive pixels of the LCD and at a low voltage to operateassociated logic circuits. The LCD display driver can output a pluralityof signals through channels for driving dots or pixels of the LCD forachieving a desired color-resolution display and a desired image movingspeed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the numbers and dimensions of the various features may bearbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic drawing showing an exemplary integrated circuit.

FIG. 2 is a schematic drawing illustrating an exemplary 10-bitresolution digital-to-analog converter (DAC) coupled with a referencevoltage generator.

FIG. 3 is a schematic drawing illustrating another exemplary DAC with a10-bit resolution.

FIG. 4 is a schematic drawing illustrating an exemplary sample and hold(S/H) circuit.

FIG. 5 is a schematic drawing illustrating an exemplary dual sample andhold (S/H) circuit.

FIG. 6 is a schematic drawing illustrating another exemplary S/H circuitcoupled with an output buffer.

FIG. 7 is a schematic drawing illustrating another exemplary dual S/Hcircuit coupled with output buffers.

FIG. 8 is a schematic drawing illustrating an exemplary S/H circuitcoupled with an output buffer.

FIG. 9 is a schematic drawing illustrating an exemplary dual S/H circuitcoupled with output buffers.

FIG. 10 is a schematic drawing illustrating another exemplary integratedcircuit.

FIG. 11 is a schematic drawing showing a system including an exemplaryintegrated circuit coupled with a processor.

DETAILED DESCRIPTION

For a conventional liquid crystal display (LCD) driver with 720channels, the conventional LCD driver uses 720 digital-to-analogconverters (DACs) for converting digital signals to analog signals. Eachof the DACs is coupled with a channel. The analog signals are output todots of the LCD, displaying images carried by the digital signals. Eachthree of the dots of the LCD can be grouped as a pixel, including ared-light dot, a green-light dot, and a blue-light dot.

It is found that the 720 DACs of the conventional LCD driver take around30% chip area of the LCD driver. If a bit-resolution of the DACsincreases, the area of the DACs expands abnormally. For example, an areaof a 10-bit resolution DAC is about 4 times of an 8-bit resolution DAC.From the foregoing, to achieve a high resolution the 10-bit resolutionDACs will consume more area of the LCD driver than the 8-bit resolutionDACs.

Based on the foregoing, integrated circuits, liquid crystal display(LCD) drivers, and systems are desired.

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of thedisclosure. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation of a feature on, connected to, and/or coupled toanother feature in the present disclosure that follows may includeembodiments in which the features are formed in direct contact, and mayalso include embodiments in which additional features may be formedinterposing the features, such that the features may not be in directcontact. In addition, spatially relative terms, for example, “lower,”“upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,”“top,” “bottom,” etc. as well as derivatives thereof (e.g.,“horizontally,” “downwardly,” “upwardly,” etc.) are used for ease of thepresent disclosure of one features relationship to another feature. Thespatially relative terms are intended to cover different orientations ofthe device including the features.

FIG. 1 is a schematic drawing showing an exemplary integrated circuit.An integrated circuit 100 can include a driver, e.g., a liquid crystaldisplay (LCD) driver, an LCD monitor drivers, an LCD display drivers, anLCD inverter, a super twist pneumatic (STN) driver, and/or other driver.For embodiments using a LCD driver with N channels, the integratedcircuit 100 can include a digital-to-analog converter (DAC) circuit 101.The DAC circuit 101 can include at least one first channel typedigital-to-analog converter (DAC), e.g., N-channel type DACs (NDACs) 101a and 101 c and at least one second channel type DAC, e.g., P-channeltype DAC (PDAC) 101 b. The DAC circuit 101 can convert digital signals,e.g., binary digital signals, to analog signals. It is noted that thechannel types of the DACs described above are merely exemplary. Inembodiments, the first channel type DAC can be PDAC and the secondchannel type DAC can be NDAC.

Referring to FIG. 1, the integrated circuit 100 can include a pluralityof sample and hold (S/H) circuits 105. Each of the S/H circuits 105 canbe coupled with one of the NDAC 101 a and 101 c and the PDAC 101 b. TheS/H circuits 105 can receive signals from the NDACs 101 a and 101 c andthe PDAC 101 b and outputting the signals in parallel. In embodimentsusing a LCD driver with N channels, the S/H circuits 105 can include NS/H circuits. Each of the S/H circuits 105 can be coupled with itscorresponding channel.

As noted, the conventional LCD driver having N channels, e.g., 720channels, uses 720 DACs for converting digital signals to analogsignals. The 720 DACs may take up about 30% chip area of theconventional LCD driver.

Unlike the conventional LCD driver, the integrated circuit 100 canmerely use 3 DACs, i.e., NDACs 101 a, 101 c, and PDAC 101 b, forconverting digital signals to analog signals. The signals output fromthe NDACs 101 a and 101 c and PDAC 101 b can be held by the S/H circuits105. At least one control signal can trigger the S/H circuits 105outputting the signals from the NDACs 101 a, 101 c, and PDAC 101 b.Since merely three DACs are used for converting digital signals toanalog signals, the chip area of the integrated circuit 100 can bedesirably reduced.

It is noted that the number of the NDACs 101 a, 101 c and the PDAC 101 bof the DAC circuit 101 described above in conjunction with FIG. 1 ismerely exemplary. In embodiments, the number of the DACs of the DACcircuit 101 can be 3n, wherein n is an integer from 1 to about 26. Themore DACs the DAC circuit 101 has, the higher speed the integratedcircuit 100 can achieve.

In embodiments, the integrated circuit 100 can include a referencevoltage generator 103 coupled with the DAC circuit 101. The referencevoltage generator 103 can provide various voltage levels to the DACcircuit 101 as reference voltages. In embodiments using a 10-bitresolution DAC, the reference voltage generator 103 can provide 2¹⁰ or1024 voltage levels.

In embodiments using a LCD driver, the integrated circuit 100 caninclude a shift register 110, a data latch 113, a sample register 115, ahold register 120, a level shifter 125, and an output buffer 150. Thedata latch 113 can be coupled with the sample register 115. The shiftregister 110 can be configured to shift start pulses of input signals(not shown). The sample register 115 can be configured to sample theshifted signals from the shift register 110. The hold register 120 canconfigured to hold the sample signals from the sample register 115. Thelevel shifter 125 can be configured to shift voltage levels of thesignals output from the hold register 120, outputting the signals to theDAC circuit 101. The DAC circuit 101 can convert the signals to analogsignals to the S/H circuits 105. The S/H circuits 105 can output theanalog signals to the output buffer 150. The output buffer 150 canoutput analog signals Y₁-Y_(N) for driving dots and/or pixels of theLCD. It is noted that the disposition and/or use of the shift register110, the data latch 113, the sample register 115, the hold register 120,the level shifter 125, and the output buffer 150 described above inconjunction with FIG. 1 are merely exemplary. The scope of the inventionis not limited thereto. It is also noted that the integrated circuit 100may include at least one decoder and at least one DAC described inTSMC2009-0331 commonly owned and assigned, and hereby incorporated byreference for all purposes.

FIG. 2 is a schematic drawing illustrating an exemplary 10-bitresolution DAC coupled with a reference voltage generator. In FIG. 2, a10-bit resolution DAC 201 can include at least one input end, e.g., 10input ends, for receiving 10-bit binary digital signals D0-D9. The DAC201 can be similar to one of the NDACs 101 a and 101 c and PDAC 101 b.The DAC 201 can receive 1024 voltage levels provided from the referencevoltage generator 203. The DAC 201 can include a plurality of switches(not labeled). Each of the switches can be controlled by one bit of the10-bit binary digital signals D0-D9. Each of the 10-bit binary digitalsignals can turn on 10 switches for coupling one of the 1024 voltagelevels to an output end of the DAC 201.

FIG. 3 is a schematic drawing illustrating another exemplary DAC with a10-bit resolution. In FIG. 3, a DAC 301 can include a plurality of rowsof serial transistors. The DAC 301 can be similar to one of the NDACs101 a and 101 c described above in conjunction with FIG. 1. Forembodiments using a 10-bit resolution DAC, the DAC 301 have 1024 rows ofserial transistors. Each row of the serial transistors can have 10transistors coupled in series. Each row of the 10-series transistors canreceive a voltage level. The DAC 301 can receive a 10-bit binary signalD0-D9. Each gate of the 10 transistors can receive one bit of the 10-bitbinary signal D0-D9. The 10-bit binary signal D0-D9 can turn on one ofthe 1024 rows of the 10-series transistors such that one of the 1024voltage levels can be output to an output end of the DAC 301. It isnoted that the N-channel transistors shown in FIG. 3 can be replacedwith P-channel transistors to form a PDAC that is similar to the PDAC101 b.

It is noted that the DACs 201 and 301 described above in conjunctionwith FIGS. 2-3 are merely exemplary. Any type of DAC, e.g., anoversampling DAC, an interpolating DAC, a Delta-Sigma DAC, an R-2R DAC,a thermometer coded DAC, a hybrid DAC, a segmented DAC, or any DAC thatis capable of converting digital signals to analog signals can be used.

FIG. 4 is a schematic drawing illustrating an exemplary sample and hold

(S/H) circuit. A S/H circuit 405 can be similar to one of the S/Hcircuits 105. In FIG. 4, the S/H circuit 405 can be disposed between abuffer 402 and an output buffer 450. An input end 402 a of the buffer402 can be coupled with a DAC, e.g., one of the NDACs 101 a and 101 cand the PDC 101 b (shown in FIG. 1). The output buffer 450 can besimilar to the output buffer 150.

Referring to FIG. 4, the S/H circuit 405 can include analog switches410, 420, and a capacitor 415. The capacitor 415 can be disposed betweenthe analog switches 410 and 420. The analog switch 410 can receive, forexample, a sample signal SN and a sample bar signal SNB for sampling asignal from a DAC. The capacitor 415 can store the sampled signal fromthe DAC through the analog switch 410. The analog switch 420 can receiveat least one control signal, e.g., a strobe signal STB and a strobe barsignal STBB for turning on the analog switch 420 outputting the signalstored in the capacitor 415 to the output buffer 450.

In embodiments, the S/H circuit 405 can include dummy analog switches430 and 440. The dummy analog switch 430 can be coupled with an outputend of the analog switch 410. The dummy analog switch 440 can be coupledwith an output end of the analog switch 420. The dummy analog switches430 and 440 can be configured to desirably reduce a charge injectionand/or clock feed-through of the analog switches 410 and 420,respectively, during a transition period of the analog switches 410 and420.

FIG. 5 is a schematic drawing illustrating an exemplary dual sample andhold (S/H) circuit. Items of FIG. 5 that are the same items in FIG. 4are indicated by the same reference numerals increased by 100. In FIG.5, a S/H circuit 505 can include analog switches 510, 520, 550, 560 andcapacitors 515, 555. The capacitors 515 and 555 can be disposed betweenthe analog switches 510 and 520 and between the analog switches 550 and560, respectively.

The analog switch 510 can receive, for example, a sample signal SN and asample bar signal SNB for sampling a first signal from a DAC. Thecapacitor 515 can store the first sampled signal from the DAC. Theanalog switch 520 can receive at least one first control signal, e.g., astrobe signal STB1 a strobe bar signal STBB1, for turning on the analogswitch 520 for outputting the first signal stored in the capacitor 515.The analog switch 550 can receive, for example, a sample signal SM and asample bar signal SMB for sampling a second signal from the DAC. Thecapacitor 555 can store the second sampled signal from the DAC. Theanalog switch 560 can receive at least one second control signal, e.g.,a strobe signal STB2 a strobe bar signal STBB2, for turning on theanalog switch 560 for outputting the second signal stored in thecapacitor 555. In embodiments, while the analog switch 520 is turned on,outputting the first signal stored in the capacitor 515, the analogswitch 560 can be turned off. The analog switch 550 can be turned on,sampling the second signal from the DAC that can be stored in thecapacitor 555. In embodiments, the S/H circuit 505 can be referred to asa dual S/H circuit. The dual S/H circuit can have a desirably enhancedoperating speed.

In embodiments, a transistor 590 can be disposed between an input end ofthe output buffer 550 and ground or supply voltage VSS. The transistor590 can be configured to receive a control signal R1. After the analogswitch 520 outputs the first signal stored in the capacitor 515 andbefore the analog switch 560 outputs the second signal stored in thecapacitor 555, the control signal R1 can turn on the transistor 590coupling the input end of the output buffer 550 with the ground orsupply voltage VSS. The coupling can reset and/or clean the voltagelevel on the input end of the output buffer 550.

In embodiments, the S/H circuit 505 can include dummy analog switches530, 540, 570, and 580. The dummy analog switches 530, 540, 570, and 580can be configured to desirably reduce a charge injection and/or clockfeed-through of the analog switches 510, 520, 550, and 560,respectively, during a transition period of the analog switches 510,520, 550, and 560.

FIG. 6 is a schematic drawing illustrating another exemplary S/H circuitcoupled with an output buffer. Items of FIG. 6 that are the same itemsin FIG. 4 are indicated by the same reference numerals increased by 200.In FIG. 6, a control signal, e.g., a strobe signal STB, can trigger anoutput buffer 650 for outputting the signal stored in a capacitor 615.In embodiments, the strobe signal STB can close a switch (not labeled),coupling the output buffer 650 with a supply voltage V_(sup) forreleasing the signal stored in the capacitor 615.

FIG. 7 is a schematic drawing illustrating another exemplary dual S/Hcircuit coupled with output buffers. Items of FIG. 7 that are the sameitems in FIG. 5 are indicated by the same reference numerals increasedby 200. In FIG. 7, control signals, e.g., strobe signals STB1 and STB2,can trigger output buffers 750 a and 750 b, for outputting signalsstored in capacitors 715 and 755, respectively. In embodiments, each ofthe strobe signals STB1 and STB2 can close a switch (not labeled),coupling the output buffers 750 a and 750 b with a supply voltageV_(sup) for releasing the signals stored in the capacitors 715 and 755,respectively.

In embodiments, the analog switch 710 can receive at least one samplesignal, e.g., a sample signal SN and a sample bar signal SNB, forsampling a first signal from a DAC. The capacitor 715 can store thefirst sampled signal from the DAC. The analog switch 750 can receive atleast one sample signal, e.g., a sample signal SM and a sample barsignal SMB, for sampling a second signal from the DAC. The capacitor 755can store the second sampled signal from the DAC. While the switchcoupled with the output buffer 750 a is closed for outputting the firstsignal stored in the capacitor 715 through the output buffer 750 a, theswitch coupled with the output buffer 750 b is opened. The second signalstored in the capacitor 755 can be held while the first signal stored inthe capacitor 715 is output. The operating speed of the S/H circuit 705can be desirably enhanced.

FIG. 8 is a schematic drawing illustrating an exemplary S/H circuitcoupled with an output buffer. Items of FIG. 8 that are the same itemsin FIG. 4 are indicated by the same reference numerals increased by 400.In FIG. 8, an output buffer 850 a can be disposed between a S/H circuit805 and an analog switch 820. The analog switch 810 can receive at leastone sample signal, e.g., a sample signal SN and a sample bar signal SNB,for sampling a signal from a DAC. The capacitor 815 can store thesampled signal from the DAC. The analog switch 820 can receive at leastone control signal, e.g., a strobe signal STB a strobe bar signal STBB,for turning on the analog switch 820 for outputting the signal stored inthe capacitor 815 through the output amplifier 850 a.

FIG. 9 is a schematic drawing illustrating an exemplary dual S/H circuitcoupled with output buffers. Items of FIG. 9 that are the same items inFIG. 5 are indicated by the same reference numerals increased by 400. Inembodiments, the analog switch 910 can receive at least one samplesignal, e.g., a sample signal SN and a sample bar signal SNB, forsampling a first signal from a DAC. The capacitor 915 can store thefirst sampled signal from the DAC. The analog switch 950 can receive atleast one sample signal, e.g., a sample signal SM and a sample barsignal SMB, for sampling a second signal from the DAC. The capacitor 955can store the second sampled signal from the DAC. While the analogswitch 920 is turned on for outputting the first signal stored in thecapacitor 915 through the output buffer 950 a, the analog switch 960 isturned off. The second signal stored in the capacitor 955 can be heldwhile the first signal stored in the capacitor 915 is output.

FIG. 10 is a schematic drawing illustrating another exemplary integratedcircuit. Items of FIG. 10 that are the same items in FIG. 1 areindicated by the same reference numerals increased by 900. As noted, S/Hcircuits 1005 can hold signals from DAC circuit 1003 such that thesignals can be output in parallel through an output buffer 1050. Theintegrated circuit 1000 can be free from including a hold register asthe hold register 120 described above in conjunction with FIG. 1.

FIG. 11 is a schematic drawing showing a system including an exemplaryintegrated circuit coupled with a processor. In FIG. 11, a system 1100can include a processor 1101 coupled with an integrated circuit 1110.The processor 1101 is capable of controlling the integrated circuit1110. In embodiments, the processor 1101 can be a processing unit,central processing unit, digital signal processor, or other suitableprocessor. The integrated circuit 1110 can be similar to one of theintegrated circuits 100 and 1000 described above in conjunction withFIGS. 1 and 10.

In embodiments, the system 1100 can include a high definitiontelevision, a vehicle, a cell phone, a set top box, a media player, apersonal computer (PC), a laptop, a notebook, a personal digitalassistant (PDA), a calculator, and/or any system.

In embodiments, the processor 1101 and the integrated circuit 1110 canbe physically and electrically coupled with a printed wiring board orprinted circuit board (PCB) to form an electronic assembly. Theelectronic assembly can be part of an electronic system such ascomputers, wireless communication devices, computer-related peripherals,entertainment devices, or the like.

In embodiments, the system 1100 including the integrated circuit 1110can provides an entire system in one IC, so-called system on a chip(SOC) or system on integrated circuit (SOIC) devices. These SOC devicesmay provide, for example, all of the circuitry needed to implement acell phone, personal data assistant (PDA), digital VCR, digitalcamcorder, digital camera, MP3 player, or the like in a singleintegrated circuit.

One aspect of this description relates to an integrated circuit. Theintegrated circuit includes a digital-to-analog converter (DAC) circuitincluding at least one first channel type digital-to-analog converter(DAC) and at least one second channel type DAC. The integrated circuitfurther includes a plurality of sample and hold (S/H) circuits, each ofthe plurality of S/H circuits being coupled with a single DAC of the DACcircuit. A number of the at least one first channel type DAC isdifferent than a number of the at least one second channel type DAC.

Another aspect of this description relates to an integrated circuit. Theintegrated circuit includes a digital-to-analog converter (DAC) circuitincluding at least one first channel type digital-to-analog converter(DAC) and at least one second channel type

DAC. The integrated circuit further includes a plurality of sample andhold (S/H) circuits, each of the plurality of S/H circuits being coupledwith a single DAC of the DAC circuit. Each of the plurality of S/Hcircuits includes a first analog switch. The integrated circuit furtherincludes an output buffer configured to receive outputs of the pluralityof S/H circuits.

Still another aspect of this description relates to a liquid crystaldisplay (LCD) driver. The LCD driver includes a shift registerconfigured to shift start pulses of input signals. The LCD driverfurther includes a sample register configured to sample the shiftedstart pulses from the shift register. The LCD driver further includes alevel shifter configured to shift a voltage level of signals from thesample register. The LCD driver further includes a digital-to-analogconverter (DAC) circuit for receiving the voltage level shifted signalsfrom the level shifter, wherein the DAC circuit includes at least onefirst channel type digital-to-analog converter (DAC) and at least onesecond channel type DAC, a number of the at least one first channel typeDAC is different than a number of the at least one second channel typeDAC. The LCD driver further includes a plurality of sample and hold(S/H) circuits, each of the plurality of S/H circuits being coupled witha single DAC of the DAC circuit. The LCD driver further includes anoutput buffer configured to receive outputs of the plurality of S/Hcircuits.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit comprising: adigital-to-analog converter (DAC) circuit including at least one firstchannel type digital-to-analog converter (DAC) and at least one secondchannel type DAC; and a plurality of sample and hold (S/H) circuits,each of the plurality of S/H circuits being coupled with a single DAC ofthe DAC circuit, wherein a number of the at least one first channel typeDAC is different than a number of the at least one second channel typeDAC.
 2. The integrated circuit of claim 1, an output buffer configuredto receive outputs from the plurality of S/H circuits.
 3. The integratedcircuit of 2, further comprising a transistor connected between an S/Hcircuit of the plurality of S/H circuits and the output buffer.
 4. Theintegrated circuit of claim 3, wherein the transistor is configured toreceive a control signal configured to selectively connect an input ofthe output buffer to a supply voltage.
 5. The integrated circuit ofclaim 2, further comprising a switch connected to the output buffer,wherein the switch is configured to selectively connect the outputbuffer to a supply voltage.
 6. The integrated circuit of claim 2,further comprising an analog switch, wherein the analog switch isconfigured to receive an output of the output buffer.
 7. The integratedcircuit of claim 6, further comprising a dummy analog switch connectedto an output of the analog switch.
 8. The integrated circuit of claim 1,further comprising a reference voltage generator, wherein the DAC isconfigured to receive a reference voltage from the reference voltagegenerator.
 9. The integrated circuit of claim 1, wherein a total numberof DACs in the DAC circuit is 3n, where n is an integer from 1 to 26.10. An integrated circuit comprising: a digital-to-analog converter(DAC) circuit including at least one first channel typedigital-to-analog converter (DAC) and at least one second channel typeDAC; and a plurality of sample and hold (S/H) circuits, each of theplurality of S/H circuits being coupled with a single DAC of the DACcircuit, wherein each of the plurality of S/H circuits comprises: afirst analog switch, and an output buffer configured to receive outputsof the plurality of S/H circuits.
 11. The integrated circuit of claim10, wherein each of the plurality of S/H circuits further comprises asecond analog switch, and the first analog switch and the second analogswitch are configured to receive a signal from a corresponding DAC ofthe DAC circuit.
 12. The integrated circuit of claim 11, wherein theoutput buffer comprises a first amplifier configured to receive anoutput of the first analog switch, and a second amplifier configured toreceive an output of the second analog switch.
 13. The integratedcircuit of claim 12, wherein the output buffer further comprises a firstswitch configured to selectively connect the first amplifier to a supplyvoltage, and a second switch configured to selectively connect thesecond amplifier to the supply voltage.
 14. The integrated circuit ofclaim 12, wherein an output of the first amplifier is connected to anoutput of the second amplifier.
 15. The integrated circuit of claim 12,further comprising: a third analog switch configured to receive anoutput of the first amplifier; and a fourth analog switch configured toreceive an output of the second amplifier.
 16. The integrated circuit ofclaim 15, wherein an output of the third analog switch is connected toan output of the fourth analog switch.
 17. The integrated circuit ofclaim 15, further comprising: a first dummy analog switch connected toan output of the third analog switch; and a second dummy analog switchconnected to an output of the fourth analog switch.
 18. A liquid crystaldisplay (LCD) driver comprising: a shift register configured to shiftstart pulses of input signals; a sample register configured to samplethe shifted start pulses from the shift register; a level shifterconfigured to shift a voltage level of signals from the sample register;a digital-to-analog converter (DAC) circuit for receiving the voltagelevel shifted signals from the level shifter, wherein the DAC circuitincludes at least one first channel type digital-to-analog converter(DAC) and at least one second channel type DAC, a number of the at leastone first channel type DAC is different than a number of the at leastone second channel type DAC; a plurality of sample and hold (S/H)circuits, each of the plurality of S/H circuits being coupled with asingle DAC of the DAC circuit; and an output buffer configured toreceive outputs of the plurality of S/H circuits.
 19. The LCD driver ofclaim 18, further comprising a hold register configured to hold samplesignals from the sample register.
 20. The LCD driver of claim 19,wherein the level shifter is configured to receive the signals fromsample register via the hold register.